Modulation



's sneets-sheet 1 MODULATION N. E. LINDENBLAD original Filed April 5, 1952` Nov. 24, 1936.

nNveN'roR' NlLS EQUNDENBLAD ATTORNEY Nzv. 24, 1936. N. vE. LINDENBLAD MODULATION Original Filed April 5; 1932 5 Sheets-Sheet 3 INVENTOR NILS E. LINDENBLAD ATTORNEY Patented Nov. 24, 1936 UNITED STATES PATENT OFFICE MODULATION .Nils E. Linaenblad, Port Jefferson, N. Y., assigner to Radio Corporation of America, a corporation of Delaware original application April 5, 1932, serial No.

603,310. Divided and this application Novem- ,man

This invention, which is a'udivision of my copending application Serial Number 603,310, iiled in the United States Patent Oflice, April 5, 1932,

relates to the short wave signaling art and apper-y tains especially to the modulation and electromagnetic propagation of ultrashort waves, particularly in the range of wave lengths below two meters and of the order of frequencies above one hundredfty million (150,000,000) cycles perv second.l

One object of my present invention is to provide a modulation'system for extremely short wave length oscillations of electrical energy.

My present inventionwill be described more -fully hereinafter from which many other objects, features and advantages of my present invention will become self apparent.

In lthe accompanying drawings,

Figure l'shows a preferred embodiment oi' my ultra short wavelength modulator;

Figure 2 illustrates a modification of the modulation'of Figure 1;

Figure 3 illustrates an alternative antenna arrangement Which may bel used with either of the systems shown in Figure 1 or 2;

. Figure 4 illustrates still another modified modulating arrangement; and,

Figures 5, 6, and 'l illustrate still other forms of my present invention.

Turning to Figure` 1, energy of fundamental frequency from any suitable source (not shown) is fed through a variable transmission lin'e formed of conductors |32, |34 of variable length 'to the anode circuit or .input circuit of the magnetic frequency multiplier MFM, which anode circuit is composed of conductors |36, |38 directly connected to thelanodes |40, |42 of my magneticv frequency multiplier MFM. Within the electron discharge devicesA or vacuum tubes |44, |46 of my frequency multiplier thereare also the control grids or electrodes |48, |50 adjacent the cathodes or filaments |52, |54 respectively. Condensers |53, |55 are in shunt Withthe filaments |52 land |54 respectively of the magnetic frequency multiplier. n

To prevent the harmonics generatedby the frequency multiplier from reacting (or losing4 energy) backwards upon the source connected to line |32, |34, the conductors |32, |34 are tied on to voltage nodal points or current maximum points or low impedance points for harmonic waves on,

the tuned anode circuit, of the frequency multiplier formed by conductors |36, |38. With respect to fundamental waves, the anode ends of the an,-

ode circuit are high voltage or high impedance trated.

v scribed, namely, without the magnetic apparastrap |56 which in turn is grounded through conductor |58. A source of potential, may, if desired, be placed in the conductor` |58 to maintain the anodesfat a suitable D. C. operating potential. However, I have found in lmany cases, i'or frequency multiplication at these extremely high frequencies, namely, for example, ofthe order of magnitude of million cycles per second, or generally, over' 100,000 kc. per second, supplied from the master oscillator or other source, that the anodes |40, |42 can be grounded as illus- 1 The output circuit of the frequency multiplier is formed of conductors |60, |62 adjustable in length and tuned to a harmonic, for example, the

third harmonic, or in other words, tuned for y frequencies of 450,000 kilocycles per second, assuming of course that the master oscillator oro'ther source, connected to lines |52, |54 is adjusted to operate at 150,000 kilocycles per second.

The cathode energizing circuit for cathodes |52, |54 of electron discharge devices |44, |46, consists in general of internal conductorsA |64, |66 insulated from and supported within the concentric yexternal tubular conductors |68, |10. Filament `heating current may be traced from conductor 58- through voltage 'regulating resistance |12 `through tuning conductor or, strap |14 through the filamentsl |52, |54 and back through the internal conductors |64, |66 conducting strap or short circuiting element |16 through conductor |18 to the other side or conductor 42 of the filament heating circuit bus supplied with energy from source 44.

By adjustment of straps |14 the cathode circuit is tuned for best matching with the rest of the circuits. 'Ihis means it has a compromise optimum for both fundamental and harmonic frequency. The grid circuit being set for optimuml impedance to harmonic energy, this energy readily feeds into and iiows through the same and builds up to a large value.4

Now, the frequency multiplier asso far detusillustrated. will not deliver an appreciable output. To increase the output, I apply a unidirectional magnetic field to the electronstream` Y' within the tubes |48, |50, -in a direction perpendieular to their normal paths o1' travel from lament to anode. The magnetic apparatus consists of a pair of solenoids |180, |82 through which runs ayoke |84, preferably of iron of all EEB 1 8 1941A high permeability `which may -or may not be 55 740 1n addition. it is to trons which travel from laminated.` The solenoids |80, |82 are serially connected as shown, and supplied through conductors |84, |88 with energizing currents from a line 42 by way vof an' adjustable resistor |88.

5 It is to be noted that the grids or electrode |48, |50 adjacent the cathodes |52, |54 are connected to the output circuit formed of conductors |80, |62, within which looped conductor tuning purposes as well as to allow the direct current voltage, generated by grid rectiiication,

across grounding resistor or biasing resistor |92 to manifest itself upon the control'grids or electrodes.

The resistor |82 is preferably so chosen that the positive peaks of input potential applied to the anodes |40, |42 cause spurts of electrons to impinge upon the control grids or grids adjacent the cathodes. Under such circumstances',l without the application of the magnetic eld, the harmonic output, if any, will bek very feeble. However, by the application of the longitudinally or axially applied unidirectional magnetic eld, the output, at harmonic frequencies in the tuned output circuit |60, |62, |90 is materially augmented and of a substantial value. j

A qualitative explanation, as well as a practical explanation of this phenomenon is electrons emanating from the iilaments are curved in their paths a`nd retained by the magnetic field in large quantities in suspension in the space about the cathodes and closely adja` cent the control grids.- Hence, when the in`- tensity of a positive peak of applied input potential has grown to suflicient strength to bring the electrons to the grids in spite of the 'curving, the number of electrons which splash against the control grids is considerably larger than that number without the suspension effect.

be pointed out that this improved action may also be due to the fact that due to' the suspending of the electrons within the space closely' adjacent the control grids, there` is less time difference between the electhe space suspension to the control grids when arrayed on curves almost tangential with the grid relative to the time diif'erence between radially arrayed electrons. These arrays are. considered in the sense of the '50 motion of the electrons and not in the sense of their actual location. involved, this time lag efiect is,.as will be eviv dent, -very important,for,/unles`s the electrons lmpinge upon the output electrodes in unison. '55 the abruptness of variation required to produce a harmonic will neve'" be obtained. -This is perhaps better understood if itis pointed out that, the higherthe frequency, the more electrons which at a certain moment are coniined in the space, represent the total number of electrons taking part in an oscillatory cycle. In other words, due

duration of a cycle relative to the electron velocity'it is very importanti in unison will overcome the handicap dueto fthe absence of missjaction which is readily ob tained at lower frequencies. l

Thus, the application the unidirectional 'magnetic field causes a sharper impigement of electrons as well as cut off of electron new to.

|90 is slidably and conductively arranged for that the t the high frequenciesv so do the fto the extremely short time have themotions of l the electrons well disciplined so that their action ping of electron flow which -is responsible to a large degree for harmonic waves.

In general also, improvement in output as well as in many cases, changefrom non-0pera.

tion tooperation, or, in other words, increased efficiency is obtained by the Vtuning of such circuits as the iilament h eating circuits.

In actual construction, I havel used with good success electron discharge deviceswith T-shaped glass envelopes, the longitudinal axes of the anodes of which are substantially parallel to the longitudinal axes of the solenoids |80, |82. Portions of the tube also have been made to extend v trodes, that is, between grids and plates,-is so` great it is immaterial whether the fundamental input is applied to the grids or the plates.

Odd harmonics are fed into'the absorption circuit or modulation link circuit AS and eventual- 1y transmitted by means of transmitting antenna.A TA.

For telegraphic` signalling, at some point intermediate the antenna and the output circuit of the frequency multiplier, known forms of keying apparatus may be inserted, or'known types of chopper wheels for that purpose.

For complex Wave modulation however, such as rvoice modulation, or multiplex signalling, it will be found that the ordinary or conventional schemes of modulation 'as already pointed out. fail because of inordinate frequencyvariation in the final output. l

Accordingly,p a'very importantfeature of my present invention yis my improved modulating system comprisingas illustrated,v the absorption circuit or systems AS and the magnetic modulator MM.

The lharmonic frequency output'isitaken from the absorption circuit, it is obvious that stand ing waves are setup thereon. To points of high and preferably maximum potential, 202, 4284, in the absorption circuit, I couple through conductors ,206, 208 the tunable control grid circuit 2|0 of electron discharge devices 2|2,2|4 forming part of my improved modulation system.

As illustrated, the tuned circuit 2 l0 consists of conductors 2 i0, 2 I8 within which and conductively in contact therewith is slidable loop 220 for tuning purposes. The conductors 2'|8,'2|8 are connected respectively to the control grids `222 and 224 of electron discharge devices 2-| 2, 2|4.

heretofore described in connection with my. frequency multiplier, I shall notl describe thesame "15 As the filament energizing or cathode energiz. ing circuit 228 o f my magnetic modulator is iden-Y tical with that of the cathodeenergizingcircuits 2,061,947" in detail again. Similarly, the magnetic appafloating, that is, left disconnected. 'Howeven if desired, a tuned circuit similar to any of the anode circuits described hereinabove, may be connected thereto. Now, it will be found that if it is attempted to modulate, with conventional schemes, the energy in the absorption circuit, for example, by by-passing that circuit to ground through a variable impedance in the form of electron discharge'devices, variations in the direct current through the impedance device in accordance with modulating potentials will produce only infinitesimal effects upon the energy in the absorption circuit. This is due to the fact that the capacitance of the device prevents any appreciable electron moving voltage to buildup at these very high frequencies. Only by careful lining up of the electrons will it be possible to make them respond to these small voltage variations. Moreover, the low electron velocity within the ordinary tubes also mitigates against their `use as modulators.

However, with my improved tube absorbing circuit comprising tubes 2l2, 2M, modulation is readily accomplished asl the characteristics of the tubes are greatly changed, with the tion of the magnetic field thereto. w

In other words, by causing the electrons to suspended in orbits near the grid, due to the effect of the magnetic field, a greater numberof electrons are available to be effected by modulating potentials.

The grids are in this case preferably supplied with a positive bias so that they at all timesgare positive. Inthis way, electrons of tangential motion versus the grid are vat all times available in great numbers in thelextreme -vicinity of the grid so that even* though low, potentials of high frequency can vspend work on the same withthe result that absorption takes place.` To vary the t potential level upon the control grids of the magnet'ic modulator, thereby varying the absorption of energy by making a; greater or smaller number j of electrons available and thereby accomplishing modulation of the Waves in the absorption circuit, incoming modulation, from asource (not shown) is applied through a transformer 234 to a' plurality of electron discharge device amplifiers u 238 connected in parallel. These audio frequency amplifiers may have their filaments energizedS by a source of alternating currents (not shown) through a transformer 238.k Anode potential is supplied through conductor 248 from a source (not shown) in which there is serially connected 'a choke coil 242 for audio frequency currents.

This choke insures the-flow of the varying amplified modulating currents through a. potentiometer 65/ or resistor 244.

The fixed or normal bias on the control grids of the, modulator tubes isA derived from resistor 244 through variable tap 246 and cnductor 248. A choke 258 is placed in series with a conductor 248 for a purpose which will be explained morefully hereinafter. I

As the tapping point 246 givinga correct D. C.

bias level' -for the grid electrodes of the mag-- netic modulator tubes may be erroneously placed as regards desired audio voltages which it is de-r applicasued to apply te the contra grida the choke :so as already indicated, has been placed in series with conductor 248. This choke prevents the flow of substantially all audio frequency currents or potentials from point 246. f A

vcontrol grids of the magnetic modulator, the de- 15 sired high audio frequency voltage and the relatively low value unidirectional polarizing poten- As already pointed out, the variations in potential on the control grids of the magnetic modulator tubes vary the amount of energy absorbed from the absorption circuit, as a result of which through adjustable coupling C-2 andtransmission line 256 thereis fed to the trans- I mitting antenna TA an amplitude modulated 5" wave of substantially constant frequency.

The transmission line construction TL follows the construction given in my copending United States patent application Serial Number 463,610, filed June 25, 1930. Brieny, the modulated har- 3 monic frequency 'carrier energy travels `through .transmission line 256 through building wall 258 over transmission lines 260. 262 and 264 to the feeder wires 214 for radiating or transmittingy antenna TA, which is provided with a smooth plane metallic reflector 212. f

1 'I'he transmitting antenna comprises a plurality of linear radiators 216 each substantially one-half wave length long arranged coaxially with each other and parallel to another group of half wave/ 40 radiators 218. The radiators 218 are also coaxial with each other parallel to the radiators 216. Asindicated, the radiators 216, 218 are formed by bending single conductors 280, 282 These-con- Aductors are so bent that alternate half wave portions thereof form radiating portionsa's indicated, lthe cross portions at 282 284 being substantially parallel and close together produce substantially. cancelling radiations.` Hence, by analysis it will be found that the instantaneous currents in the radiating portions 216, 218 are in like phase as a result of which a bi-directional radiant characteristic isV obtained. This bi-directional characteristlc is reduced to a unidirectional character-` istic by placing a metallic reflector 212 behind the plane formed by theradiating conductors 216, 218 i which are arranged in the same linear plane.l The `spacing between the antenna system and the smooth metallic reflecting sheet 212 is preferably made substantially one-quarter ,wavelength al-` though any substantially odd quarter wave length spacing will produce the desired result. By means of insulators, the radiators may be supported upon the reflector, the insulators being fixed to voltage nodal points -on the conductors, for example, the midpolnts of radiators 216. 218 andthe cross-over points of the conductors 260, 282.

To concentrate the beam, several radiating systems may be placed one aboye the other as illustrated. Energization is accomplished through the common feed line 214 as is apparent from an inspection of the drawings. This feed line'214 is formed of a' pair of conductors as illustrated, short circuited at their far ends, the input feed from K transmission line 264 being'at a point of relatively 76 l is in a more or less straight line.

30 located in a similar tower.

.'40 tem.

45 magnetic frequency multiplier by way of a circuit 352 from a source 334 which,

55 MFM, from 65 desired to produce.

input points to the antenna sections are of low impedance. The aforementioned short circuits are a quarter wave beyond the working length of 5 the feed line 214 thus forming a high` impedance suspension link.

Because of the extremely' short wave lengths involved. propagation follows the optical laws fairly close. Consequently, radiation in general, The reflector and antenna may be tilted at any angle so as to project, say, a beam of waves upon a smooth plane reflector situated, say, on the top of a high tower. The reflector mounted on the tower will in turn l5 reflect the wavesl at an angle of reiiection'equal to the angle of incidence thereon. For example, a ,transmitting antenna TA may be pointed to a reflector on top of a tower some 500 feet high. The reflector may be so positioned that the vbeam is y propagated horizontally until due to the curvature of the earth, it approaches the surface of the earth. At this point another reflector may be provided to say, turn the direction of the beam at right angles to the directionupto that point, to

a suitable receiver located at some distant point.

Preferably, however, due to unavoidable lossesv during reflection, I prefer to place the transmitting antenna as high as possible and at a receiving station which may or may not be One may also build up systems of curved reflectors with common foci or wire systems with refractive properties, etc.

For repeating any form of bi-direction antenna may be used, for example, if an antenna has two main characteristic ears the one can be used for the incoming signal and the other to'repeat it/in another direction; Even unidirectional antennae `may be used provided the incoming and repeated signals are on the same side ofthe antenna sys-V A modified form of my invention for modulating waves ofthe order in frequency of 450,000 kilo-l cycles per second; is illustrated in Figure 2.

Filament heating or energizing energy for the MFM 4is supplied though illustrated as a battery, may obviously be any form of unidirectional current. Unidirectional current, of course, for this purpose is preferred 50 although A. c. types of camente. maybe utilized.

One end of the filament energizing source is grounded as shown at 333. Y

Fundamental, frequency energy i's applied to the anodes of themagnetic frequency multiplier a suitable source (not shown) connected to the line or conductors 344, 343'. Tuning of the anode circuit of the magnetic frequency. multiplier tubes 343, 343'may be accomplished as in Figure 1 by variation of adjustable slides -in 80 the anode circuit not shown. The heatingcircuit 332 of the magnetic .frequency multiplier MFM the rest of the cir\' cuit. This tuning may or may not be either the is tuned for best matching for fundamental or harmonic frequency which it is The magnetic field, longitudinally applied to. the tubes 343, 343 inthe arrangement shown in Figure 2 is accomplished by the action of solenoids 334, 353 which may be wrapped about'or simplyplaced about the tubes 343, 343. Moreover, if

desired, the-solenoids may be provided with magnetic cores or the magnetic arrangementmay f* Y takethe form described in connection with mgure u 1; The intensity'of the magnetic field is, of course,

point it directly -43'3 i8 PrOvided.

source 333 and resistor 332'.

, The coupling from circuit AS to the absorber or modulator vtubes 403 and 433 is shown in a simplified way. Through the action of resistor 33S suitable grid bias is maintained upon the grids of the tubes 343, 343, the resistor being connected to a short circuiting conductor 338 variable along the conductors 313, 312 forming part of the circuit AS as well as thel tuned grid circuit. The gridV circuit as in Figure 1, forms the output circuit of the magneticjfrequency multiplier, thelsho'rt circuiting strap 333 being connected as indicated across voltage nodal points; on the circuit AS whereas the conductors 314, 313 connected to the circuit AS through bypassing condensers 313,333are connected to this circuit at voltage maximum points 31|, 313

thereon, or'in other words, at high impedancel long relative to the wave length landclue to the relative location of these wires and their relative phase, it will be found that energy is propagated predominantly along the bisector of the angles formed by theconductors 334, 383. The attenuation in the conductors at the high frequencies involved is so great for wires 100 waves long, that there is. substantially no reection, as a result of which no reflector formed of a similar pair of conductors, is required.`

'Ihe antenna line TL may be coupled as illustrated in Figure 3 to pairs pf conductors similar to 334,- 333, each pair, of lcourse, being arranged in a different plane. In Figure 3, the conductors 33,4, 333 are in one plane whereas conductors 333, 330 .are in another plane. -These pleines may be the horizontal orA vertical planes or any planes intermediate the two. 'Ihe transmitting antenna TAof Figure 2 may, of course, bearranged in either a horizontal or've'rtical plane, and the antenna system of Figure 3 may be rotated'any angle about the bisector of the solid angle formed by the conductors.

Modulation, as already indicated,v is accomplished by absorbing variable amounts of energy corresponding to amplitudes of the modulating potentials, from circuit 15S by means of modulator or absorber tubes 433, 433. In particular, amplified modulating potentials from, for example, microphone 332, .are fed to an audio amplifier 334, which, through. the action of transformer- 333, impresses those potentials through conductor 333 short circuiting 'strap 433 and conductors 432, 434, to the grid of electron discharge devices 433, 433 of my magnetic modulator. To make doublysu're no fimdamental energy gets through and becomes modulated to give back reaction, short` circuiting conductor To maintain proper upon magnetic modulator MM, a unidirectional source of potential 4 I3 is provided. As before,

the cathode energizing circuit 4I3 of the magnetic modulator MM is tuned. The anodes of electron discharge devices 403, 433 of the magnetic modulator. maybe left Meeting that is,

bias upon a control grid completely disconnected. or short circuited by vshort circuit 4 I2. However, if desired, circuit 4I2 may be tuned to the harmonic or, in other words, to the same frequency as that to which the absorption circuit AS, MM is tuned.

The solenoids 4I4 are energized by a source l4| 8 -and produce a unidirectional magnetic eld which, of course, is applied to the electron flow within the modulator tubes 406, 408.

As I have already pointed out, my improved allel connected modulator tubes 420.l Direct cur-- rent potential for both the modulator tubes 420, the magnetic modulator MM, for which, by the way, the magnetic apparatus has been omitted Vao for the sakeof simplicity, is supplied through conductor 422. The modulator reactor 424 is chosen so as to have practically no D. C. reresistance. Consequently, the grids and filaments ofthe modulator tubes 426, 428 will be at the same D. C. potential except fonthe drop in D. C. potential across resistor 430. However, since the current drawn through choke 424 is constant through'its inherent action, the voltage across resistor 432 connected between the anodes and cathodes of ,the modulator tubes 420, will vary according to the modulating potentials due to the varying current ows therein. Consequently, the voltage upon the grids of the modulator tubes 426, 428 will vary as a result vof which varying amounts of current will be drawn from the absorption circuit AS.- i

'I'he arrangement shown in Figure 4 offers the advantage that blocking condensers, such as ycondenser 254 of Figure 1, in a 'modulation circuit is unnecessary. Moreover, this arrangement shown in Figure 4 has the added advantage that, because of resistancevcoupling, Atlie circuit is extremely stable, is of fine iidelity', and greatly simplifies operation.

Although'I have shown the lament tuning conductors to lbe the means for conveying heating currents to the filaments of the various tubes,

heating currents may be supplied through choicesl to the filaments, the tuning conductors in that case carrying only high frequency currents and if desired blocked off from the .heating currents by means of large blockingcondensers.

My present invention, however, is not limited to push-pull tube arrangements. but may be applied equally as well to single tube arrangements. Also it is not limited to amplitude modulation. For example in Figure 5 I have illustrated diagrammatically an' arrangement wherein single tube stages are utilized and wherein the` ensuing output is frequency modulated.

The arrangement shown-in Figure 5 utilizes a master oscillator MO supplying an improvedsingle tube magnetic frequency multiplier MFM whose output is frequency modulated and fed to.

a suitable transmitting antenna TA.

Cathode heating energy fr the cathode of the master oscillator tube 500 is supplied through concentric conductor 502, tubular in form, and internal` conductor 504 after being impressed thereon through the medium of transformerill. The potentiometer 5I5 is really not needed if the potentiometer 5H is present in the grid circuit. v

The iilament-of tube 500 maybe heated by direct current and the arrangement shown in connection with tube 528 maybe used whereinv lthe potentiometer 569' serves the dual purpose of regulating cathode bias kand cathode heating current. It is to be clearlyy understood that either arrangement may be used on either tube.

The slider 508 contacting with tube 502 and slidable along grounding strip Iiiil,l (see Figure 6) in turn fastened to grounding plate 5I2 insulatby means of the condenser dielectric strip M8, is

' ingly separated from the shield or container 5|4 used to tune or adjust the impedance of the cathode high frequency circuit formed by the tube 502 and in effect ground 5I4. I

A similar sliding arrangement 5|8 is used to tune the grid circuit comprising linear conductor High frequency oscillations generated by the master oscillator are fed :from the anode 522 through the adjustable tuning trombone 524, D. C.

blocking condenser or radio frequency by-passing condenser 530 to the input electrode or anode 528 of the magnetic frequency multiplier tube 528.

erates similarly to the magnetic frequency multipliers hereinabove described and is provided withl a solenoid 540 in order to apply longitudinally of the tube 5,28, a unidirectional magnetic field. The output electrode 542 is the normal grid electrode or electrode adjacent the cathode of the tube 528 and is tuned to a harmonic of the input frequency by means of slider 558. The cathode circuit of the magnetic frequency multiplier is adjusted in impedance by means of a slider 568 so that the potentials arising thereon have the most beneficial phase relation forv harmonic production in the output circuit including conductors 556'and capacitively grounded strip"554. 'I'he output conductor 510 is tapped to a point 512 in the output circuit for most eiilcient energy trans-- ergy m`ay be obtained by Simply varying the voltage on any of the cold' electrodes of the magnetic frequency multiplier and/or master oscillator..` The frequency variation thus obtained is at these very high frequencies very much greater in magnitude than the inherently ob? tainedamplitude modulation. For this purpose, in connection'withFigure 5, the voltage on the cold electrode 542 vof -the magnetic frequency multiplier, is wobbled lby means of transformer 518 supplied with alternating currents from a suitable source 580 andkeyed by means of a keyer 582i. This alternating voltage from source 580 is superimposed upon 'the unidirectional voltage impressed upon, cold electrode 542.

Similar results could be obtained byy inserting the transformer 518 in the anode lead of tube 528, or in theahode or control electrode leads of the master oscillator tube '500, or, in connection with the pushpull arrangements, any similar polarizing leads. It is/also to be clearly understood that the source of alternating currents 580 and the keyer 582 may be replaced by a micro also be applied in series with the source of energy energizing the solenoid 540 for modulating purposes.

In the event that it is desired to radiate from linear radiator 514 an amplitude modulated wave, an absorption system employing the principles hereinbefore delineated is preferably utilized.

Should it be desired to use a. push pull absorption scheme, the output circuit may be arranged as shown in Figure 7.

Then, the output trombone 516,y is connected to output inductor loop 580 grounded by means of conductor 582. 'I'he antenna 514 is coupled to the loop 580 by adjustable loop 582 and ad- Justable transmission line 584. For amplitude modulation purposes, energy may be drawn from linel as illustrated by the tube arrangement heretofore described. l

Although various modifications of my present invention have been described, it is not limited thereto since many changes will readily suggest themselves to those skilled in the art. For this reason and since it would be impractical to illustrate every modification of my present invention, it should be clear that it is not to be restricted by the exact descriptions and illustrationsgiven,

but solely by the breadth of the appended claims.`

Having thus described my invention, what I claim is:

1. In a modulating system comprising a circuit having high frequency currents flowing therein, and, an electron discharge device having an electrede 'adjacent its cathode connected to said circuit -for varying the flow of currents in said circuit, the method of varying the amplitude of current flowing in said circuit which includes varying the voltage on said electrode adjacent the cathode of said device, in accordance with variations to be imparted to the high frequency currents nowing in said circuit, and, subjecting the electron stream within said deviceto a unidirectional magnetic held.

2. A system for absorbing high frequency energy from ahigh frequency circuit comprising an -electron discharge device having an velectron emitting cathode, and a control electrode, a circuit connecting said control electrode to said high frequency circuit, and a circuit connected with said control electrode for varying the potential on said control electrode whereby said vcontrol elec-` trode-cathode circuit absorbs energy from said high frequency circuit in accordance with the varying potential applied to said control electrode.

3. In combination, a tuned high frequency circuit having a high frequency voltage maximum point, and means for varying the now of high frequencycurrentsin said circuit at a relatively low frequency rate comprising an absorbing circuit connected to said high frequency circuit at said voltage maximum point, said absorbing circuit comprising the impedance between the cathode and a cold electrode in an electron discharge device, said cathodev emitting electrons to said cold electrode and means for subjecting the emitted electrons to a unidirectional magnetic field.

4. A modulating system comprising a'high frequency circuit having voltage maximum points, said circuit having flowing therein high frequency currents to be modulated, a pair of electron discharge devices each having an electron emitting cathode and a cold electrode, means connecting said cold electrodes to voltage maximum points in. said high frequency circuit, means for subjecting the electron streams within said devices to unidirectional magnetic action, and, means for varying the conductivity of said devices thereby 5 varying the amount of energy diverted from said high frequency circuit.

5. Apparatus as claimed in claim 4 wherein the cathodes of said devices are connected together by a circuit tuned t0 a frequency corresponding l0 pair of electron discharge devices each having an l5 electron emitting cathode, and, a cold electrode; a tuned circuit connecting said cold electrodes togather and to. a point on said high frequency circuit, a circuit including a reactance to said high frequency `oscillations connecting said cathodes 20 together, circuits connecting a point on said high frequency circuit and a point on said last named circuit to points of similar radio frequency potentials and means for applying a magnetic field to the electron streams within said devices.

7. In a modulating system comprising a circuit having high frequencycurrents flowing therein, and, an electron discharge device having an electrode adjacent its cathode connected to a point on said tuned circuit for varying the ow of cur- 3U rents'in said circuit, the method of varying the amplitude of current flowing in said circuit which includes varying the voltage on said electrode adjacent the cathode of said device, in accordance with modulating potentialsto be impressed on 3 5 the high frequency currents flowing in said circuit, and simultaneously subjecting the electron stream in said device to a unidirectional magnetic field of substantially constant strength perpendicular to the path of said electron stream.`

8. Modulating apparatus to be used with a high frequency circuit comprising an electron discharge device including an electron emitting cathode and an auxiliary electrode, a circuit connecting said auxiliary electrode to said high fre# 4x5A quency circuit and to apoint of substantially fixed radio frequency potential, a circuit connecting said electron emitting cathode to a point of substantially fixed radio frequency potential.

means to tune said last named circuit to res- 50 onance at the frequency of said high frequency circuit, whereby said cathode' oscillates at said high frequency relative to said point of xed potential,y and means for applying modulating potentials to said auxiliary electrode.

9. Means for modulating ultra high frequency oscillations comprising an electron discharge device having an electron emitting cathode and an auxiliary electrode, a circuit connecting said isis auxiliary electrode to a. point of substantially fixed 5 0 radio frequency potential, means for tuning a portion of said last named circuit to resonance at the'frequency of said ultra high frequency to be modulated, a tuned circuit connecting said cathode to said point of fixed radio frequency 35 potential whereby relative oscillations at said ultra high frequency between at least one of said electrodes and said point is produced, and means for applying modulating potentials to the auxiliary electrode.v Y

10. Modulating apparatus comprising a pair ofY electron discharge devices each having an electron emitting'cathode and an auxiliarytelectrode, circuits connecting the auxiliary electrodes of said discharge devices together and to a point of subgether and to a point of substantially xed radio frequency potential, means for tuning each of said last named circuits to resonance at ultra high frequency, whereby said cathodes oscillate relative-to said point of substantially fixed radio fre'- quency potential, and a circuit for applying modulating potentials between said auxiliary electrode and said. cathode.

11. Modulating apparatus as recited 'in claim 10, in which the circuits connecting said auxiliary electrodes together are each turned to resonance to ultra high frequency.

12. Modulating apparatus as recited in claim 8, including means for producing va magnetic field of substantially i'lxed strength in the Apath along which the electrons emitted by when energized ow.

13. Modulating apparatus as recited in claim 8, in which a source of potential is connected to said electron emitting cathode by .way of said circuit connecting :said cathode to a point of substantially xed radio frequency potential.

14. In a modulating system to be used with a high frequency circuit, an electron discharge de- `said cathode lvice including an electron emitting cathode and an auxiliary electrode, a circuit connecting said auxiliary electrode to said high frequency circuit and to a point of substantially fixed radio frequency potential, a circuit connecting said electron emitting cathode to a point of substantially fixed radio frequency potential, a reactance in said last named tcircuit which offers a high impedanceto the flow therein of oscillations of a frequency of the order of the frequency to which said ultra high frequency circuit is tuned, and means for applying modulating potentials to saidauxiliary electrode.

15. A modulating system as recited inclaim 14 in which a capacity and inductance is included in said last named means.

16. In'amodulating system to be used with an ultra high frequency circuit, an electron clischarge device including an electron emitting cathode and an auxiliary electrode, a circuit connecting said auxiliary electrode to saidultrahigh frequency circuit and tb a pointv of substantially fixed radio frequency potential, a circuit connecting said electron emitting cathode to a pointy of substantially fixed radio frequency potential, a reactance in said last named circuit of high impedance to oscillations of a frequency of the order of the frequency of said first named circuit, means for applying modulating potentials to said auxiliary electrode, and means for 'applying a magnetic' fleld to the electron stream within said device.V Y

' 17. A modulating apparatus as recited in claim 10 including means for applying a magnetic field lof substantially fixed strength to the electron streams within said devices.

18. In a signalling system, a first tuned high frequency circuit, an electron discharge device having an electron emitting electrode and a gridv likeelectrode in the emission pathof said emitting-electrode, a second tuned circuit connecting said grid-like electrode to a point on said tuned high frequency circuit, an impedance connecting a different point on said tuned high frequency circuit to a point of xed high frequency potential, a third tuned circuit of high impedance to oscillations of the frequency to which said rst named circuit is tuned connected between said i electron emitting electrode and said point of fixed high frequency potential, a source of heating current for said emittingelectrode connected to said third named circuit and means for varying the impedance of said device at signal frequency.

19. In a signalling system, a tuned high freq'uency circuit, a pairy of electron discharge devices, each having an electron emitting electrode and a grid-like electrode in the emission path of said emitting electrode, a second tuned circuit connecting said grid-like electrodes to spacedY points on said first named high frequency circuit, an impedance connecting different points on said high frequency circuit to a point of fixed high frequency potential, a third tuned circuit of high impedance to oscillations of the frequency to which said first named tuned circuit isV tuned, connected between sa'id electron emitting electrodes andsaid point of fixed high frequency potential, a source of heating current for said emitting electrodes connected to said third named circuit and means for varying the impedances of said electronl discharge devices at signal frequency.

20. In a signalling system a tuned high frequency circuit, a pair of electron discharge devices,'each having an electron emitting electrode, a grid-like electrode in the path of emission of said emitting electrode and a plate-like electrode, a second tuned circuit connecting said grid-like electrodes to spaced`points on said first named high frequency circuit, an impedance connecting different points on said first named high frequency circuit to a point of fixed-high frequency potential, a third tuned circuit, of high impedance to oscillations of the frequency to which said iirst named tuned circuit is tuned, connected between said electron emitting electrodes and said point of Afixed high frequency potential, a source of. heating current for said emitting electrodes connected 'to said third named circuit, a circuit of low impedance connected between said platelike electrodes and means for varying the impedance of said devices at signal frequency.

21. A signalling'system asvrecited in claim 19 in which the impedances of said devices are varied in phasev at signal frequency. y

22. A signalling system as recited in claim 2 wherein the impedances of said devices are varied in phase at signal frequency. 

